Peaking circuit



G. D. FORBES 2,443,790

PEAKING CIRCUIT Filed April 26, 1944 June 2 2, 1948.

IN VEN TOR.

GORDO N D FORBES ar rey Patented June 22, 1948 TENT OFF IEE d claims.

I 1 This invention relates to'a communicationsystem and particularlyto a system'forthe forma- "tion of sharp pulses. In radar and television systems, as 'well asih general'applications, it frequently becomes necessary togenerate a sharp pulse'having a" shorttime duration. U sually such "pulses may be generated from a rectangular'voltage Wave by so-called peaking or diiferentiating circuits consisting of a combination of resistance and capacitance or resistance-and inductance, having a time constant small incomparison to the shortest period of the component frequencies involved." -I-Iowever; in many practical instances, the voltage wave available forpeaking may be far from rectangular due to frequency characteris- "17165 of the circuit; particularly characteristics caused by the presence of largenamounts of distributed capacitance. Under such-circumstances the usual peaker circuits will not provide desired peaken-action. This invention provides asystem wherein an effective peaker action is obtained over a wide range of input voltage wave forms.

A related circuit is disclosed in my co-pending application, Serial No. 518,154, filed Jan. 13, 1944.

The invention in general provides for a pulse transformer associated with a delay line and rectifier in such a fashion that the desired action takes place. In order thatthe invention may be more fully understood, reference will now be made to the figures diagrammatically showing the invention.

In Fig. '1, an input circuit in and H has a coupling condenser l2 and a primary I3 of a pulse transformer 14 connected therein as shown. Pulse transformer I4 is of the type well known in this art, comprising a transformer having comparatively small primary and secondary windings disposed over a laminated core of thin metal sheets. The transformer is characterized by very low distributed capacitance and low leakage reactance and may cover a band of frequencies whose upper limit may be of the order of 75,000 or even 100,000 cycles per second. The transformer ratio, as a rule, is quite low and in this instance may be unity. The secondary I5 is connected to terminal l6 and ll of the output circuit. For convenience, terminals II and H may both be grounded.

Connected across windings l3 and I5, these being in series for this purpose, is an inductance having such a value and having such distributed capacitance as to constitute a delay line having an accurate predetermined delay, such as for example t; microsecond. Connected in shunt acrossdelay line 20 is a-diode Y2l'. shown here, the diode is connected-With' its anode-'22 on the input side of the 'delayline and cathode 23 on the output side. This. may=berreversed,rhowever, inwhich case thesystem:.will.operate in a manner reverse to the systenr as shown.

Fig. 2 shows an alternative view of the transformer of Fig. 1. "Similar. points and connections have beensimilarly designated as prime numbers.

Ihesystemis. adapted tobe supplied with-the voltage pulses'availa-ble forxpeaking. Such pulses may rhave'any desirediduration and. may represent thesvoltagepulsesz present in various :por-

tions of aradar system or may actually represent 'thetenvelope of the detected. output of a large targetv echo.: .For convenience, the. voltage pulse is shown as negative incharacter, although this iaimmaterial.

i The. operation is as follows. The initial drop in voltage passes through coupling condenser l2 which is preferably of a small value. The negative voltage front passes down through primary 13 of the pulse transformer to ground. This induces a voltage in secondary l5 of substantially the same valueand about the same shape. However, the polarity of secondary I5 is such that terminal [6 is positive with respect to ground. At the same time, the negative voltage wave passing through delay line 20 (the polarity is such that diode 2| is non-conducting) also reaches output terminal l6. Thus, in output I6, there is generated first a positive voltage and then about t; microsecond later, the negative voltage from delay line 20 appears to complete a pulse having a time duration of about 6 microsecond.

The tail of the rectangular voltage pulse applied to input ll! may, as far as diode 2| is concerned, be considered as a positive voltage. Thus diode 2| becomes conducting. This, in combination with the action of pulse transformer l4, serves to efiectively suppress the operation of the system on a voltage rise in the positive direction. In fact, the rise of voltage in a positive sense will tend to be dissipated by going through "windings l3 and [5, the magnetic fields tending 3 transformer M has been assumed to be unity, it may be desirable to depart from this somewhat to compensate for losses or suppress any tendency ,for oscillations. Thus, some pulse shaping may a voltage variation in a positive sense so that r the next cycle may occur. Furthermore, a small capacitanc will tend to prevent any floating action of the condenser with respect to ground.

It is clear that if diode 2! is reversed, the system will operate in the same manner except that potential variations in a positive sense will be peaked while potential variations in a negative sense will be suppressed.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent is:

1. In a system of the character described, a pulse transformer having a primary and secondary, an input circuit connected across the primary, an output connected across the secondary, said primary and secondary having one terminal of each in common, a delay line connected across the other input and output terminals and forming a shunt across the seriesconnected primary and secondary of the transformer, and a rectifier connected across said delay line, said system being adapted to be fed by recurring voltage pulses and yielding an output consisting of a voltage peak for one side of each input pulse.

Number 4 2. A peaking circuit including a transformer having a primary and secondary, an input circuit connected across said primary, an output circuit connected across said secondary, and a delay line connected between one end of said primary and one end of said secondary, said circuit being adapted to be fed by recurring voltage pulses and yielding an output of peaked voltage pulses.

3. In a system of the character described, a transformer having primary and secondary windings, one terminal of each winding being connected together, a delay line connected between the other terminals of the windings to transmit an impulse applied to said other terminal of said primary winding to said other terminal of said secondary winding, delayed and opposite in polarity to the impulse induced on said other terminal of said secondary winding by said applied impulse through said transformer, and, rectifier means connected across said transformer to short circuit impulses of one polarity.

4. In a system of the character described, a delay line, and a transformer having a primary and a secondary winding, means to apply an impulse to said primary and said delay line to transmit to said secondary a delayed pulse opposite in polarity and closely following the impulse induced in said secondary, and rectifier means connected to said transformer to short circuit impulses of one polarity.

GORDON DONALD FORBES.

REFERENCES CITED The followingreferences are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,224,134 Blumlein Dec. 10, 1940 

